This revised R34 application proposes the development and initial evaluation of a school-based, indicated, preventive intervention for high-school aged adolescents who are at risk for social anxiety disorder (SAD) and/or depression and who display a common risk factor, interpersonal difficulties with peers, as reflected in elevated levels of interpersonal peer victimization (IPV). Among adolescents, SAD and depression are prevalent, highly comorbid, and can be chronic and impairing. IPV is a key stressor that contributes to both social anxiety and depression in adolescents; it includes relational (e.g., social exclusion) and reputational (e.g., spreading rumors) forms of peer victimization. Currently, there are no preventive interventions for adolescent SAD. Also, effective preventive interventions for adolescents have not yet integrated a focus on both social anxiety and depression or targeted specific peer risk factors. Interventions for depression and for bullying have not addressed IPV, which is less observable than overt victimization (e.g., threats, physical acts). Given adolescents' extensive use of technology, cyber forms of IPV represent a critical but understudied issue that also will be addressed. Specifically, the Peers Emotions and Relationships (PEERS) intervention, will take an integrated approach to reducing risk for SAD and depression by modifying and adapting an evidence-based intervention for depression, Interpersonal Psychotherapy for Adolescents (IPT-AST), that focuses on improving interpersonal skills and managing conflict. We will add elements of anxiety-based treatments (e.g., exposures, managing threat perception) and strategies for handling challenging peer experiences. PEERS will have a positive focus and will target adolescents who report elevated symptoms of social anxiety and/or depression and high levels of IPV. The development and preliminary evaluation of PEERS will occur across two phases. In Phase 1 we will: a) review key elements of IPT-AST, and add additional strategies for dealing with social anxiety and for coping with IPV experiences; b) conduct focus groups with 16 adolescents and 16 school personnel for input on program development, content, and presentation; c) screen adolescents to identify 16 at-risk adolescents who will participate in an open trial of PEERS to refine the intervention; and d) manualize PEERS. Phase 2 is a pilot randomized trial of PEERS versus education support (ES). We will screen adolescents to identify and enroll 48 at-risk adolescents who will be randomly assigned to PEERS or ES. Measures will evaluate the feasibility and acceptability of PEERS, rates of attrition, and the preliminary impact of PEERS versus ES on adolescents' symptom severity for social anxiety and depression and their IPV experiences. We will examine the durability and persistence of PEERS' effects at 6-month follow-up. PEERS will be the first preventive intervention for adolescent social anxiety and will make an important contribution to the literature on indicated preventive interventions for adolescent IPV and depression. The public health impact of PEERS is enhanced by conducting this work in schools with a predominantly minority population.